cooler, nutrient-rich deeper waters. The deeper waters contain high levels of
nitrates and phosphates, which result from the decomposition and sinking of
surface water plankton. When these nutrients are brought to the surface through
upwelling, they supply necessary nutrients for phytoplankton, which form the
base of the oceanic food chain.
Figure 2.15 UpwellingLa Niña (Cool Phase)
The steps of forming a La Niña are:
■ Trade winds that blow west across the tropical Pacific are stronger than
normal.
■ This results in an increase in the upwelling off of South America.
■ This then results in cooler-than-normal sea surface temperatures off of
South America.
■ This leads to wetter-than-normal conditions across the Pacific Northwest,
and both drier- and warmer-than-normal conditions in the southern United
States, which results in an increase in the number of hurricanes.
■ Winter temperatures are warmer than normal in the southeastern United
States and cooler than normal in the northwest.
■ This also causes heavier-than-normal monsoons in India and Southeast
Asia.